Robot overload detection mechanism

Abstract

An overload detection mechanism for a robot is disclosed, wherein first and second members are relatively urged together by an urging means to urge the axis of the second member toward the Z axis of the first member. The second member is guided in any movements departing from coaxial alignment, and the first member is supported near the end of a robot arm. A tool mount or workpiece mount is connected to the second member. An electrical device is mounted on one of the members, and a device actuator on the other of the members, with the reaction means acting between the members to relatively move the members upon tilting from an X-Y plane normal to the Z axis, or axial thrust applied by the tool mount to the second member. In this manner, an overload of a tool in the tool mount establishes relative movement between the first and second members, so that the electrical device is actuated to change an electrical condition thereof and can be connected to stop movement of the robot.

What is claimed is: 
     
       1. An overload detection mechanism for a robot arm comprising, in combination: a first member having a Z axis;   a second member having a second axis;   urging means acting between said members to urge said members toward axial alignment on said Z axis;   guide means to guide said second member in movements departing from coaxial alignment on said Z axis;   means to support said first member near the end of a robot arm;   means to connect said second member to a tool mount for the end of a robot arm;   an electrical device mounted on one of said members and a device actuator on the other of said members; and   reactions means acting between said members to relatively move said members upon thrust along a Z axis, or movement in an X-Y plane normal to said Z axis, whereby due to overload on said second member said first and second members are relatively moved and said electrical device is actuated to change an electrical condition thereof.   
     
     
       2. An overload detection mechanism for a robot arm as set forth in claim 1, wherein said second member is disc-shaped. 
     
     
       3. An overload detection mechanism for a robot arm as set forth in claim 1, wherein said urging means is a mechanical spring. 
     
     
       4. An overload detection mechanism for a robot arm as set forth in claim 1, wherein said electrical device is a switch connected to stop the movement of the robot arm. 
     
     
       5. An overload detection mechanism for a robot arm as set forth in claim 1, wherein said electrical device is a proximity switch. 
     
     
       6. An overload detection mechanism for a robot arm as set forth in claim 1, wherein said electrical device is a linear variable displacement transducer to determine the amount of overload movement. 
     
     
       7. An overload detection mechanism for a robot arm as set forth in claim 1, wherein said reaction means includes a plurality of depressions in one of said members substantially equally spaced around said Z axis and a plurality of reaction elements one each receivable in a respective depression and acting on the other of said members to be responsive to torque overload around said Z axis. 
     
     
       8. An overload detection mechanism for a robot arm as set forth in claim 7, wherein said depressions are V-shaped depressions. 
     
     
       9. An overload detection mechanism for a robot arm as set forth in claim 7, wherein said reaction elements are pins with conical ends to engage respective depressions. 
     
     
       10. An overload detection mechanism for a robot arm as set forth in claim 1, wherein said guide means includes a housing fixedly attached to said first member and housing said second member. 
     
     
       11. An overload detection mechanism for a robot arm as set forth in claim 10, wherein said second member is a disc having first and second faces, and said housing has a cylindrical opening receiving said disc. 
     
     
       12. An overload detection mechanism for a robot arm as set forth in claim 11, wherein said housing has a first face opposing said disc first face and an annular surface opposing said disc second face. 
     
     
       13. An overload detection mechanism for a robot arm as set forth in claim 12, including tapered depressions in said disc second face and said reaction means are pins carried in said housing annular surface. 
     
     
       14. An overload detection mechanism for a robot arm as set forth in claim 13, wherein said urging means is a compression spring acting between said first faces. 
     
     
       15. An overload detection mechanism for a robot arm as set forth in claim 1, wherein said urging means is a pneumatic piston and cylinder. 
     
     
       16. An overload detection mechanism for a robot arm as set forth in claim 1, including a compound slide movable in said X-Y plane and connected to move said second member. 
     
     
       17. An overload detection mechanism for a robot arm as set forth in claim 1, including housing means as a part of said support means and mountable on the end of the robot arm, said housing means containing said first member. 
     
     
       18. An overload detection mechanism for a robot arm as set forth in claim 1, including a first housing as a part of said support means and mountable on the end of the robot arm. 
     
     
       19. An overload detection mechanism for a robot arm as set forth in claim 18, including a second housing as a part of said support means and axially slidable in said first housing. 
     
     
       20. An overload detection mechanism for a robot arm as set forth in claim 19, wherein said guide means is a cylindrical aperture in said second housing and contains said first and second members. 
     
     
       21. An overload detection mechanism for a robot arm as set forth in claim 20, wherein said first and second members are disc-shaped and urged together by said urging means. 
     
     
       22. An overload detection mechanism for a robot arm as set forth in claim 19, wherein said first and second housings are urged apart by said urging means. 
     
     
       23. An overload detection mechanism for a robot arm as set forth in claim 21, wherein said second member has a lever arm connected to one face of the disc, with said lever arm extending along said second axis and movable by an overload condition. 
     
     
       24. An overload detection mechanism for a robot arm as set forth in claim 22, wherein said connection means includes a platform movable in said X-Y plane and connected to move said lever arm second axis off said Z axis upon an overload condition.